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Abstract
Spin-lattice relaxation times have been measured for various non-equivalent carbon-13 nuclei on the surface of quasi-spherical hydrocarbon molecules, and the results indicate the isotropy of molecular reorientation in the pure liquids. Variations in carbon-hydrogen bond lengths affect significantly the corresponding dipolar relaxation times as expected. At ambient temperatures, the molecular dynamics conform to a diffusional model. Translations and rotations are only weakly coupled. The Kivelson parameter % has values in the range 0·07–0·10. The reorientational correlation times, τe, extrapolated to zero viscosity agree with those calculated under the assumption of free rotation. The reduced orientational correlation times display a very good linear dependence upon the reduced temperatures derived from the boiling points for norbornadiene, 2-methylene norbornene, α- and β-pinene. This empirical relationship consists of a single line for these four hydrocarbons. The points corresponding to other globular systems, for which values of τe are known at various temperatures, such as CCl4, CDCl3, or ClOF3, merge into it. Its generality might make it an extremely useful property.
Trochilics (science of rotatory motion (Roget's Thesaurus of English Words and Phrases, 312)) of small reporter molecules, Part III; Part I: Jauquet, M., and Laszlo, P., 1972, Chem. Phys. Lett., 15, 600; Part II: Grandjean, J., Laszlo, P., and Price, R., 1973, Molec. Phys., 25, 695.
Trochilics (science of rotatory motion (Roget's Thesaurus of English Words and Phrases, 312)) of small reporter molecules, Part III; Part I: Jauquet, M., and Laszlo, P., 1972, Chem. Phys. Lett., 15, 600; Part II: Grandjean, J., Laszlo, P., and Price, R., 1973, Molec. Phys., 25, 695.
Notes
Trochilics (science of rotatory motion (Roget's Thesaurus of English Words and Phrases, 312)) of small reporter molecules, Part III; Part I: Jauquet, M., and Laszlo, P., 1972, Chem. Phys. Lett., 15, 600; Part II: Grandjean, J., Laszlo, P., and Price, R., 1973, Molec. Phys., 25, 695.